It is known to provide an inflatable vehicle occupant protection device, such as an airbag, for helping to protect an occupant of a vehicle. Airbags are deployable in response to the occurrence of an event for which occupant protection is desired, such as an impact to the vehicle, a vehicle collision, a vehicle rollover, or a combination thereof. Frontal collisions refer to collision events in which a vehicle experiences an impact at the front of the vehicle. These frontal collisions cause front seat vehicle occupants to move forward in the vehicle toward structures, such as the steering wheel (driver side occupant) and/or the instrument panel (passenger side occupant).
Frontal collisions of a vehicle can occur as a result of the vehicle travelling forward into an object, such as another vehicle, a tree, a pole, etc. Frontal collisions can also occur as a result of a stationary vehicle being impacted at the front by another vehicle. Frontal collisions can further occur as a result of two or more moving vehicles moving toward each other in a “head on” impact.
To help protect occupants of vehicles involved in frontal collisions, the vehicle can be equipped with driver frontal airbags. On the passenger side of the vehicle, driver frontal airbags are typically deployed from a housing located within the instrument panel of the vehicle. Because the occupant on the passenger side is not charged with operating the vehicle, the passenger driver frontal airbag can be configured to cover a large area in front of the front passenger seat, i.e., the instrument panel, windshield, etc., and can extend laterally, in both outboard and inboard directions in the vehicle, for example, from adjacent or near the passenger door to adjacent or near the centerline of the instrument panel or even beyond.
The inflatable volume of passenger frontal airbags increases with the coverage that the airbag provides. Passenger airbags also typically have a substantial depth, so as to optimize the cushioning effect it has on an impacting occupant. Passenger frontal airbags need to reach the inflated and deployed condition within a predetermined amount of time, which is a fraction of a second. To do this, the inflator is sized to deliver inflation fluid at a volumetric flow rate that will result in deployment of the airbag within the required time. All of these factors must be considered and balanced when configuring a passenger frontal airbag system. There are limitations on inflator size (the volume of inflation fluid delivered by the inflator and the rate at which it is delivered) and, because of this, the configuration of the airbag (coverage, depth, volume, etc.) has to be matched and balanced accordingly. As a result, it can be desirable to optimize the passenger airbag in terms of coverage and depth, given the capabilities of the inflator.
On the driver side of the vehicle, driver frontal airbags are typically deployed from a housing located within the steering wheel. Because the occupant on the driver side is charged with operating the vehicle, the driver frontal airbag has to be configured with this in mind. For example, the operator may not be steering the vehicle in a straight forward direction at the time of the collision and, therefore, the steering wheel can be rotated when the airbag deploys. Because of this, steering wheel mounted airbags typically have a round/circular cushion configuration that coincides with the position and attitude of the steering wheel. Additionally, the driver frontal airbag must be configured taking into account that the operator of the vehicle will likely have one or both hands on the steering wheel at the time a collision takes place. Because of this, the steering wheel mounted airbag can be configured to have a diameter that is selected to provide adequate frontal impact protection while avoiding airbag deployment into contact with the operator's hands and arms.
One particular type of collision for which an airbag may be deployed can be referred to as an oblique collision. Oblique collisions are considered generally to be any non-frontal, i.e., any non-zero degree angle, vehicle collision. In its simplest form, a frontal, zero degree angle vehicle collision would involve a vehicle impacting, for example, a flat brick wall when the vehicle is travelling at a straight forward direction perpendicular to that wall. As a result of this impact, the occupant would move forward in a direction parallel to the vehicle axis and the direction of forward vehicle travel into contact with the deployed airbag. From this, it follows that an oblique collision, i.e., a non-frontal or non-zero angle collision, would be any collision scenario that results in the occupant moving relative to the central vehicle axis and direction of forward vehicle travel in a direction that is not parallel to the axis of straight forward vehicle travel.
Oblique collisions can occur in a variety of scenarios. For example, a vehicle travelling in a straight forward direction colliding with an angled surface, such as another vehicle oriented in a non-parallel manner, would be considered an oblique collision. As another example, an offset collision in which a vehicle collides with an object, such as another vehicle, that is offset laterally would be considered an oblique collision. This would be the case, for instance, in a vehicle collision in which the front passenger side bumper strikes the rear driver side bumper of another vehicle. As a further example, vehicles colliding when travelling in directions that are not parallel, i.e., at an angle, would be considered an oblique collision.
Additionally, in oblique collision scenarios causing forward-inboard movement of a seatbelt restrained occupant, whether a driver seat occupant or a passenger seat occupant, the movement of the occupant is in a direction that escapes the shoulder belt portion of the seatbelt. By “escapes,” it is meant to refer to the fact that the shoulder belt restraint extends downward and inward from the outboard shoulder across the torso and around the inboard hip. This being the case, forward-inboard occupant movement can cause the occupant's torso to slip out from behind the shoulder belt, thereby becoming partially unbelted or unrestrained.
Oblique collisions produce occupant movements in the vehicle that are also oblique, that is, the occupant moves obliquely relative to a central axis of the frontal airbag, i.e., an axis that extends through a longitudinal centerline of the airbag, which extends parallel to the longitudinal axis of the vehicle. This oblique movement can be forward-outboard (i.e., toward the door) or forward-inboard (i.e., toward the vehicle centerline). Forward-outboard movement of an occupant in response to an oblique collision can be handled through the deployment of known side or lateral airbag structures, such as side curtains, door mounted side airbags, seat mounted side airbags, pillar mounted side airbags, etc. Conventional airbag structures do not, however, cover for forward-inboard movement of the occupant. Additionally, forward-inboard moving occupants can escape the shoulder belt portion of the seatbelt, which presents further challenges.
Furthermore, prior to “escaping” in response to forward-inbound movement, the seatbelt can act on the occupant and apply restraining forces that alter the occupant's movement. For example, the seatbelt engages the occupant's outboard shoulder and, in response to the forward-inboard occupant movement, can cause the occupant to rotate toward the outboard side of the vehicle as he or she escapes the belt. As a result, the occupant can also be subjected to rotational forces that produce rotational occupant movements during an oblique vehicle collision.
Moreover, because the passenger airbag necessarily occupies a comparatively large volume, it can be challenging to provide the desired area of coverage within the necessary airbag deployment time. Since the passenger airbag is typically deployed centrally from the instrument panel, i.e., directly in front of the passenger side occupant, it can be difficult to configure the airbag to also expand laterally to provide adequate coverage for the passenger side occupant in the case of an oblique collision, while at the same time meeting deployment time requirements.